In industrial systems, and particularly, in refrigeration and air conditioning systems, the mixing of water with liquid refrigerants is undesirable. For example, the presence of excess water in liquid refrigerants may freeze at low temperatures and restrict or completely prevent the flow of expansion valves, capillary tubes, and the like.
In addition, the solubility of amounts of refrigerant in liquids such as water is of considerable concern in refrigeration systems such as drinking water coolers, water cooled condensers and the like where small amounts of the refrigerant are introduced with water or other liquids either through equipment failure, or in some instance, by faulty design. The presence of excess water in halogen may cause corrosion in the system. In particular, such water may cause the hydrolysis of leaky halogenated refrigerant with the formation of acids. These acids tend to corrode metals as well as insulation and other nonmetallic parts of the system. This condition is especially problematic during charging of the refrigeration system. Accordingly, detection of the halogen contaminant is essential to the operation and maintenance of these systems.
Refrigerant loss imposes an expense in at least two ways. First, the unit cost of a refrigerant is high and the total replacement cost of the lost refrigerant, particularly from large commercial refrigeration and air conditioning systems, can be very expensive. Secondly, if a refrigeration system fails due to refrigerant loss, there is the possible spoilage and loss of the refrigerated contents. It is desired to detect the existence of the refrigerant leak before the refrigerant loss has become great enough to degrade equipment performance. Further, leakage of refrigerants and in particular those comprising halogen may well degrade the environment.
In a typical refrigeration or air conditioning system, there are at least first and second loops. The first is a closed loop for circulating a refrigerant, typically a well known halogen refrigerant. The first, refrigerant loop includes a motor-driven compressor for compressing the inputted halogen, thus converting the halogen refrigerant from a gaseous to a liquid state and outputting a heated halogen liquid. The heated halogen is supplied to a condenser, which cools the halogen liquid. Typically, such condensers include a serpentine shaped tube, typically made of copper, for receiving and circulating the warm liquid halogen, and a shell for enclosing the serpentine shaped tube and circulating water thereabout, whereby the liquid halogen is cooled. The cooled liquid halogen is next directed through an expansion valve and into an evaporator. As the halogen changes from a gaseous to a liquid state, it absorbs heat thereby providing significant cooling. The cooled halogen gas is returned through the first loop from the evaporator to the compressor, whereby this cycle continues.
A trouble point in such refrigeration systems occurs in the condenser when the water circulating over the copper tubing wears by friction between the water and the tubing, holes in the tubing, thereby causing a mixing of the halogen and water. Most (but not all) refrigerants are circulated in the first, refrigeration loop under positive pressure so that when a leak occurs in the condenser tubing, halogen will flow into the cooling water and mix in the water therein. The second loop in which the cooling water flows varies from refrigeration system to refrigeration system. In some systems, the cooling water may be drawn from a river and after cooling returned to the river. In other refrigeration systems 10 such as shown in FIG. 1, the cooling water may be passed from a condenser 12 via a circulating conduit 16a to a cooling tower 14 and allowed to fall down over a series of baffles. Typically, such water towers are open to the atmosphere, whereby if there has been a halogen leak, the flow of water and halogen is exposed to the atmosphere with possible damage to the environment and in particular to the ozone layer. As shown in FIG. 1, the flow is returned from the cooling tower 14 to the condenser 12.
In those refrigeration or air conditioning systems where the refrigerant is maintained under a negative pressure, water will be drawn through the holes into the first refrigerant loop. Thereafter, the flow of water and halogen is returned from the evaporator to the condenser. Significant cooling of that flow takes place in the evaporator, whereby the water is converted to ice. When that ice is introduced into the compressor, the ice may readily damage the compressor and its motor, thereby bringing the operation of that refrigeration system to a halt.
Alternatively, there are refrigeration or air conditioning systems which incorporate an evaporator acting as a heat exchange device, whereby the expanding halogen gas passes through the evaporator in the form of a serpentine shaped coil surrounded by a shell for receiving a liquid, typically water, to be cooled. The water circulating over the evaporator tube may cause holes to wear therein, whereby a mixing of the halogen and water occurs. In such an embodiment, the cooled water is typically circulated through a second closed loop to cool an environment and thereafter return to be recooled by the evaporator. As described above, the presence of water and halogen is particularly corrosive. In those instances where the refrigerant is positively pressurized, halogen will be forced through the tube holes into the second closed cooling loop, thus contaminating the circulated water. Eventually, there is a strong possibility that the second loop will be corroded to the extent that holes will develop therein, whereby the water contaminated with halogen will leak directly into the surrounding environment. Again, possible contamination of the environment is likely.
In either of the above described refrigeration systems, wearing and contamination may occur with the result that water may become contaminated with the halogen. Therefore, it is important to be able to detect the presence of halogen mixed with water so that contaminated refrigeration systems may be shut down as early as possible and detected leaks of halogen repaired.
In U.S. Pat. No. 5,115,666, which is assigned to the assignee of this invention, there is disclosed a method of detecting halogen in a sample of halogen and a liquid by introducing that sample into a test chamber and heating that sample to a temperature dependant upon the solubility of the liquid in halogen to provide a vapor solution of halogen and liquid. The sample is subjected to an evaporation temperature selected to minimize the liquid portion of the vapor solution. The vapor solution is conveyed to a gas detector, which operates to detect a concentration of the halogen gas above a threshold level. Illustratively, that detector may comprise the detector described in U.S. Pat. No. 4,910,463, which is assigned to the assignee of this invention and which is incorporated herein by reference.
Heating samples of a halogen gas and a liquid has proven by continued observation to release a relative small percentage of the halogen gas disposed into the liquid. Further, it has been observed that calibrated samples of water with a known quantity of a test gas, e.g., a refrigerant has not yielded consistent measurement results by the use of the detector described in U.S. Pat. No. 4,910,463. Further, the introduction of consecutive cycles into the test chamber described in U.S. Pat. No. 5,115,666 without a cleansing of that test chamber, would lead to the contamination of the second sample and possible false gas concentration readings of the sample taken from a second source or zone.